The Sessions, a candid, gentle film about a paralyzed man’s quest to have sex, walks a tricky, balanced, grave and funny path that’s all its own. Struck by polio at a young age, Mark O’Brien (John Hawkes) lives mostly in an iron lung; he can get out for a few hours at a time, his assistant pushing him on a gurney. Three assistants are key in the film: Amanda (Annika Marks), a pretty young woman with whom Mark falls in love; Rod (Hawkes’ fellow Deadwood alum W. Earl Brown), who has the late shift; and Vera, whose tightly pulled-back braid and ill-chosen glasses can’t really hide Moon Bloodgood’s beautiful face. Vera, dry and warm and endlessly understanding, is Mark’s assistant when he decides he wants to have sex, and her practical acceptance of Mark’s desires sets the film’s tone.

But first, Mark, who was raised Catholic, wants to clear things with Father Brendan (an excellent William H. Macy). Given Mark’s particular circumstances, is it OK to have sex outside of marriage? Will God understand? Brendan, who’s pretty sure he’s out of his depth, is inclined to say yes.

Mark’s confessions — which are more like conversations — with the priest give The Sessions a winding, lovely shape, dotted with voiceovers and able to deftly return to certain moments and scenes. Hawkes, a marvelous actor who’s been getting his due since his malevolent, unstable turn in Winter’s Bone, is wry and self-deprecating as Mark, and Macy, a scrappy and shaggy priest, pulls an earthy spiritualism to the surface.

And then there’s Helen Hunt, who plays Cheryl Cohen Greene, the sex therapist who begins to work with Mark. In a tattered Massachusetts accent and long, flowy child-of-the-’70s clothes, Hunt is more likable, more believable and more vulnerable than ever. Writer-director Ben Lewin and his actors strike just the right balance in the scenes with Mark and Cheryl, which are often intercut with scenes in which Vera tries, gently and dryly, to explain to a perplexed motel clerk exactly what’s going on in these therapy sessions. His disbelief and skepticism are understandable, but have no weight next to the intimate, careful, kind exchange between Cheryl and Mark.

The Sessions has time and patience for all its characters, whose lives loop and tangle with each other, all woven around Mark. There are no pat morals to this story; to treat it like a reminder to appreciate what you have would be to undermine Mark O’Brien as a character and a person, and Lewin is too smart for that. Each of the film’s characters has a complex relationship with intimacy, whether a priest with his congregation, a wife with her husband or child, a caregiver with her charge or a man with his lover. Lewin’s thoughtful screenplay makes his characters equals, even Susan (Robin Weigert, yet another Deadwood alum), who appears late in the film as a hospital volunteer who makes a vital connection with Mark. “I’m not a virgin,” he tells her impulsively. In Lewin’s film, sex is a different kind of big deal: complicated, vital, vulnerable, honest — words that apply to The Sessions as well.